A flat panel display possesses advantages of being ultra thin, power saved and radiation free. It has been widely utilized. A present flat panel display mainly comprises a LCD (Liquid Crystal Display) or an OLED (Organic Light Emitting Display).
An OLED possesses many outstanding properties of self-illumination, no requirement of backlight, high contrast, ultra-thin, wide view angle, fast response, applicability of flexible panel, wide range of working temperature, simpler structure and process. The OLED is considered as next generation flat panel display technology.
Generally, OLED comprises a substrate, ITO (Indium Tin Oxide) transparent anode located on the substrate, a Hole Injection Layer (HIL) located on the ITO transparent anode, a Hole Transporting Layer located on the Hole Injection Layer, an emitting material layer (EML) located on the Hole Transporting Layer, an Electron Transport Layer (ETL) located on the emitting material layer and a Cathode located on the Electron Injection Layer. For promoting the efficiency, the emitting material layer is generally applied with co-host system.
OLED can be categorized as PM-OLED (Passive matrix OLED) and AM-OLED (Active matrix OLED).
A thin film transistor (TFT) has been widely utilized as a switching element and a driving element in an electronic device. Specifically, with the possible formation of the thin film transistor on a glass substrate or a plastic substrate. Therefore, they are commonly employed in display field, including a LCD, an OLED, an EPD and etc.
As shown in FIG. 1, which is a diagram of a structure of a thin film transistor backplane in an AM-OLED according to prior art, comprising a substrate 100, a gate 110, a gate insulation layer 120, a semiconducting layer 130, an etching stopper layer 140, a source/a drain 150, a protective layer 160, a flat layer 170, a pixel electrode 180, a pixel defining layer 190, a photospacer 200 and etc. The present manufacture method of a thin film transistor backplane in an AM-OLED is: respectively forming the gate 110, the gate insulation layer 120, the semiconducting layer 130, the etching stopper layer 140 with four photolithographic processes. Then, the source/the drain 150 are formed with one photolithographic process and then, the protective layer 160 and the flat layer 170 are formed. With another photolithographic process, the pixel electrode 180 is formed. At last, the pixel defining layer 190 and the photospacer 200 are formed. Certain disadvantages exist in the manufacture method of the thin film transistor backplane in the AM-OLED. Mainly, it can be understood that the formation of each layer requires one photolithographic process (Every photolithographic process comprises manufacture processes of thin film, photo, etching, stripping and etc.) The more the photolithographic process is required, the process time takes longer and the yield of the production becomes lower; with more numbers of processes, the more considerable accumulated yield problem is. In the mean time, the structure of the thin film transistor backplane manufactured according to the aforesaid present manufacture method of the thin film transistor backplane in the AM-OLED utilizes the pixel electrode 180 bridging the source/the drain 150, then the contact resistance exists which can cause influence to the efficiency of the AM-OLED. Besides, the overlap of the pixel electrode 180 bridging the source/the drain 150 will occupy an area of the partial pixel and cause the aperture ratio dropping.